Oygenate treatment of dewaxing catalyst for greater yield of dewaxed product

ABSTRACT

Fischer-Tropsch hydrocarbon synthesis using a noncobalt catalyst is used to produce waxy fuel and lubricant oil hydrocarbons from synthesis gas derived from natural gas. The waxy hydrocarbons are hydrodewaxed, with reduced conversion to lower boiling hydrocarbons, by contacting the waxy hydrocarbons, in the presence of hydrogen, with an unsulfided hydrodewaxing catalyst that has been reduced and then treated by contacting it with a stream containing one or more oxygenates.

This application claims the benefit of U.S. Provisional Application60/416,950 filed Oct. 8, 2002.

BACKGROUND OF THE DISCLOSURE

1. Field of the Invention

The invention relates to hydrodewaxing hydrocarbons over an unsulfideddewaxing catalyst treated with oxygenates. More particularly theinvention relates to the catalyst and to producing dewaxed fuel andlubricant oil fractions, from waxy hydrocarbons synthesized by reactingH₂ and CO produced from natural gas in the presence of a Fischer-Tropschcatalyst, by hydrodewaxing the waxy hydrocarbons over an unsulfideddewaxing catalyst that has been treated by contacting it withoxygenates.

2. Background of the Invention

Fuels and lubricants are made by incorporating various additives intobase stocks, which typically comprise dewaxed hydrocarbon fractionsderived from waxy hydrocarbons that boil in the desired fuel andlubricant oil ranges. Dewaxing reduces the pour and cloud points of thewaxy hydrocarbons, to acceptable levels. The relatively pure waxy andparaffinic hydrocarbons synthesized by the Fischer-Tropsch process arean excellent feed for producing diesel fuel, jet fuel and premiumlubricant oils with low sulfur, nitrogen and aromatics contents. Thesulfur, nitrogen, and aromatics content of these waxy hydrocarbons isessentially nil and the raw hydrocarbons can therefore be passed toupgrading operations, without prior hydrogenation treatment. In aFischer-Tropsch process, H₂ and CO react in the presence of ahydrocarbon synthesis catalyst to form waxy hydrocarbons. Those waxyhydrocarbon fractions that are solid at ambient conditions are referredto as Fischer-Tropsch wax and typically include hydrocarbons boiling inboth the fuels and lubricant oil ranges. However, they have cloud andpour points too high to be useful as fuels and lubricant oils and musttherefore be further processed (e.g., dewaxed) to meet acceptably lowlevels of cloud and pour points. Solvent dewaxing cannot be used,because the yield of dewaxed hydrocarbons boiling in the distillatefuels range will be substantially reduced and the higher molecularweight (e.g., C₁₆₊) hydrocarbons comprising the lubricant oil fractionsare typically solid at ambient temperature. Various processes have beendisclosed for catalytically dewaxing waxy hydrocarbons. Many, such asthose employing a ZSM-5 catalyst, dewax by hydrocracking the waxyhydrocarbons to products boiling below the fuel and lubricant oilranges. Others include hydroprocessing for removal of heteroatoms,aromatics and other unsaturates. Illustrative, but nonlimiting examplesof various catalytic dewaxing processes are disclosed in, for example,U.S. Pat. Nos. 6,179,994; 6,090,989; 6,080,301; 6,051,129; 5,689,031;5,075,269 and EP 0 668 342 B1.

More recently, catalysts that dewax mostly by isomerization have beendiscovered (as disclosed in, for example, in U.S. Pat. No. 5,075,269)and these produce greater dewaxed product yield, due to less cracking.However, even the best of these catalysts have some cracking activityand concomitant dewaxed product loss. Catalyst having a high crackingactivity are especially undesired for the dewaxing of hydrocarbons thatdo not contain high amounts of waxes, e.g., because they have beenproduced using a non-cobalt Fischer-Tropsch catalyst. Sulfiding adewaxing catalyst may reduce its cracking activity, as is well known inthe art, but sulfiding may contaminate both the dewaxed product thehydrogen reaction gas passing through the dewaxing reactor. It would bean improvement to the art if an alternative catalyst treatment could befound that does not require sulfiding and that does still give goodhydrodewaxing results even with waxy hydrocarbons that do not containhigh amounts of waxes. Also, the catalyst should have a reduced crackingactivity during hydrodewaxing the hydrocarbons produced by noncobaltFischer-Tropsch hydrocarbons synthesis, and thereby increase itsisomerization dewaxing activity and contaminant dewaxed product yield.

SUMMARY OF THE INVENTION

It has now been found that waxy hydrocarbons produced from aFischer-Tropsch hydrocarbon synthesis process using a noncobaltcatalyst, including fuel and lubricant fractions, can be hydrodewaxedwith reduced conversion to lower boiling hydrocarbons, using anunsulfided catalyst that has been reduced and then contacted with anoxygenate-containing hydrocarbon.

In one embodiment the invention relates to (a) producing a synthesis gasfrom natural gas, (b) reacting the H₂ and CO in the gas in the presenceof a noncobalt Fischer-Tropsch catalyst, at reaction conditionseffective to synthesize waxy hydrocarbons comprising fractions boilingin the fuels and lubricant oil ranges, and (c) passing at least aportion of the waxy hydrocarbons to an upgrading facility in which theyare hydrodewaxed with hydrogen and an unsulfided catalyst that has beencontacted with an oxygenate-containing hydrocarbon. A process in whichnatural gas is converted to synthesis gas which, in turn, is convertedto hydrocarbons, is referred to as a gas conversion process. Thus, thisembodiment relates to a gas conversion process plus product upgrading byhydrodewaxing.

The hydrodewaxing process comprises contacting the waxy hydrocarbonswith hydrogen and a dewaxing catalyst that has been treated bycontacting the catalyst with a hydrocarbon containing one or moreoxygenates. Alternatively, a waxy hydrocarbon to be hydrodewaxed andcontaining one or more oxygenates may be contacted with the dewaxingcatalyst. The dewaxing catalyst may be reduced and left unsulfided andis preferably both reduced and unsulfided. This treatment reduceshydrodewaxed product loss due to feed conversion to lower boilinghydrocarbons, by reducing the cracking activity of the dewaxing catalystand is conducted either in-situ or ex-situ of the hydrodewaxing reactor.Experiments have shown that an oxygenate treated hydrodewaxing catalyst,e.g. a ZSM-48 hydrodewaxing catalyst, is equivalent to one that has beensulfided with respect to feed conversion to lower boiling hydrocarbonsand lower methane make. As used herein, ZSM-48 includes EU-2, EU-11 andZBM-30, which are structurally equivalent to ZSM-48.

The noncobalt Fischer Tropsch catalyst refers to a catalyst wherein theactive catalyst component is a metal other than cobalt including atleast one of Fe, Ni, Ru, Re and Rh.

The hydrocarbon containing the one or more oxygenates used for thetreatment will comprise at least a portion of the waxy hydrocarbonssynthesized over the Fischer Tropsch catalyst and may or may notcomprise the waxy hydrocarbon feed to be hydrodewaxed. The term“oxygenate” refers to water and oxygen-containing compound(s) which formwater under hydrodewaxing conditions. The oxygenate(s) used during thetreatment may comprise water or one or more oxygen containing molecules,which preferably comprise functional groups containing hydroxyl, monoand polyhydric alcohols, esters, ethers, ketones, aldehydes, carboxylicacids and mixtures thereof and preferably including one or morealcohols. They may be indigenous to the waxy hydrocarbons synthesizedover the catalyst in the Fischer-Tropsch hydrocarbon synthesis reactor,and/or they may be added to it for the treatment. When the oxygenatetreatment uses water as the oxygenate, water is added after the dewaxingcatalyst has been reduced. The continuing presence after the treatment,of the treatment oxygenates in the feed being hydrodewaxed, has noadverse effect on the catalyst, the hydrodewaxing reaction or thehydrodewaxed product. Thus an oxygenates-containing, waxy hydrocarbonfraction produced by a catalyzed Fischer-Tropsch hydrocarbon synthesisreaction, may be used for the catalyst treatment and then hydrodewaxedwith no adverse effect resulting from the continuing presence of theoxygenates in the wax. In the examples below, a preferred hydrodewaxingcatalyst, ZSM-48, was successfully treated with anoxygenates-containing, raw Fischer-Tropsch wax and also with anoxygenates-containing Fischer-Tropsch light oil having an end boilingpoint of about 525° F. (274° C.), each of which was synthesized over anon-shifting cobalt hydrocarbon synthesis catalyst.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the hydrogenolysis to beta scission ratio for the treatedcatalyst of the invention compared to the untreated catalyst.

FIG. 2 compares gas make as a function of feed conversion for a treatedand an untreated catalyst.

FIG. 3 compares the 700° F.+(371° C.) hydrodewaxed oil yield as afunction of pour point, for a treated and untreated catalyst.

FIG. 4 shows the hydrogenolysis to beta scission ratio similaritybetween a treated and a sulfided catalyst.

FIG. 5 shows the gas make similarity for both a treated and a sulfidedcatalyst.

FIG. 6 is a graph comparing the extent of 700° F. (371° C.) conversionat a given pour point for both a treated and a sulfided catalyst.

FIG. 7 shows the gas make at various 700° F. (371° C.) conversion levelsfor oxygenated light oil and wax treated catalysts.

FIG. 8 shows the pour point at various 700° F. (371° C.) conversionlevels for oxygenated light oil and wax treated catalysts.

DETAILED DESCRIPTION

The dewaxing catalyst for hydrodewaxing of waxy feeds may be eithercrystalline or amorphous. Crystalline materials are molecular sievesthat contain at least one 10 or 12 ring channel and may be based onaluminosilicates (zeolites). Zeolites used for oxygenate treatment maycontain at least one 10 or 12 ring channel. Examples of such zeolitesinclude ZSM-5, ZSM-11, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-57,ferrierite, EU-1, NU-87, ITQ-13, and MCM-71. Examples of molecularsieves containing 12 ring channels include zeolite beta, ZSM-12, MCM-68,ZSM-18, mordenite, faujasite and offretite. It should be noted that adewaxing catalyst such as ZSM-5 can have altered dewaxing properties byadjusting catalyst properties, such as acidity, metal dispersion andcatalyst particle size as noted in U.S. Pat. No. 6,294,077. Themolecular sieves are described in U.S. Pat. Nos. 5,246,566, 5,282,958,4,975,177, 4,397,827, 4,585,747, and 5,075,269. MCM-68 is described inU.S. Pat. No. 6,310,265. MCM-71 and ITQ-13 are described in PCTpublished applications WO 0242207 and WO 0078677. Preferred catalystsinclude ZSM-48, ZSM-22 and ZSM-23. Especially preferred is ZSM-48. Themolecular sieves are preferably in the hydrogen form. Reduction canoccur in situ during the dewaxing step itself or can occur ex situ inanother vessel.

Amorphous dewaxing catalysts include alumina, fluorided alumina,silica-alumina, fluorided silica-alumina and silica-alumina doped withGroup 3 metals. Such catalysts are described for example in U.S. Pat.Nos. 4,900,707 and 6,383,366.

The dewaxing catalysts are bifunctional, i.e., they are loaded with ametal hydrogenation component, which is at least one Group VI metal, atleast one Group VIII metal, or mixtures thereof. Preferred metals areGroup VIII metals. Especially preferred are Pt, Pd or mixtures thereof.These metals are loaded at the rate of 0.1 to 30 wt. %, based oncatalyst. Catalyst preparation and metal loading methods are describedfor example in U.S. Pat. No. 6,294,077, and include for example ionexchange and impregnation using decomposable metal salts. Metaldispersion techniques and catalyst particle size control are describedin U.S. Pat. No. 5,282,958. Catalysts with small particle size and welldispersed metal are preferred.

The molecular sieves are typically composited with binder materials thatare resistant to high temperatures and may be employed under dewaxingconditions to form a finished dewaxing catalyst or may be binderless(self-bound). The binder materials are usually inorganic oxides such assilica, alumina, silica-aluminas, binary combinations of silicas withother metal oxides such as titania, magnesia, thoria, zirconia and thelike and tertiary combinations of these oxides such assilica-alumina-thoria and silica-alumina magnesia. The amount ofmolecular sieve in the finished dewaxing catalyst is from 10 to 100,preferably 35 to 100 wt. %, based on catalyst. Such catalysts are formedby methods such spray drying, extrusion and the like. The dewaxingcatalyst is used in the unsulfided form. The dewaxing catalysts are alsopreferably in the reduced form.

A further description of the dewaxing catalysts is exemplified by thepreparation and use of a ZSM-48 zeolite which is a preferred embodiment.A dewaxing catalyst comprising a ZSM-48 zeolite component and ahydrogenation component is known and disclosed, for example, in U.S.Pat. Nos. 4,397,827; 4,585,747; 5,075,269 and EP 0 142 317, thedisclosures of which are incorporated herein by reference. A ZSM-48zeolite is a medium pore size, acidic crystalline silica-aluminamolecular sieve, having a ten sided ring pore structure and is preparedwith an organic directing agent. After preparation it is converted tothe hydrogen form by ion exchange and calcination. In making a catalystuseful in the process of the invention, the hydrogen form ZSM-48 zeoliteis composited with a binder and or matrix component and, if desired, oneor more additional porous catalyst support components which willpreferably not adversely effect its isomerization activity or increaseits cracking activity. Such components may comprise, for example,silica, alumina and preferably non-acidic gamma alumina, non-acidicforms of amorphous and crystalline silica-aluminas, clays such asbentonite and kaolin, and the like. The hydrogenation component maycomprise at least one Group VIII metal component and preferably at leastone noble Group VIII metal component, as in Pt and Pd. Noble metalconcentration will range from about 0.1-5 wt. % of the metal, and moretypically from about 0.2-1 wt. %, based on the total catalyst weight,including the ZSM-48 zeolite component and any binder or other supportor matrix component used in the catalyst composite. The Group VIIIreferred to herein refers to Group VIII as found in the Sargent-WelchPeriodic Table of the Elements copyrighted in 1968 by the Sargent-WelchScientific Company. The one or more hydrogenation components may bedeposited on, composited or ion-exchanged with, the ZSM-48 or othercomponents or a composite of same, by any suitable means. Such means areknown and include, for example impregnation or ion-exchange. The ZSM-48catalyst used in the examples below comprised the hydrogen form ofZSM-48, an alumina binder and a noble metal as the hydrogenationcomponent. An aqueous solution of a decomposable salt of the metal wasimpregnated onto the ZSM-48 zeolite/alumina composite, followed bycalcining to decompose the salt to the metal. The resulting catalyst wasthen reduced in hydrogen prior to the oxygenate treatment of theinvention. The reduction and/or subsequent treatment can be achievedeither in-situ in the isomerization reactor or ex-situ in a separatevessel.

The ZSM-48 catalyst is reduced, preferably with hydrogen, prior to theoxygenates treatment. The one or more oxygenates used to treat thecatalyst may be carried in a hydrocarbon and the treatment comprisescontacting the reduced catalyst with a hydrocarbon stream containing theone or more oxygenates. The hydrocarbon carrier, which in an embodimentof the invention is at least a portion of the hydrocarbon productsynthesized by a Fischer-Tropsch hydrocarbon synthesis reaction, may ormay not comprise the feed to be dewaxed. All or a portion of theoxygenates used for the treatment may be added to the hydrocarbon orthey may be indigenous to it. For example, raw, untreatedFischer-Tropsch light oil and wax typically contain indigenousoxygenates, formed as a consequence of the synthesis reaction. Thislight oil or wax can be used to treat the catalyst and the wax can thenbe hydrodewaxed by the treated catalyst.

One aspect of the invention has been demonstrated using raw (untreated)Fischer-Tropsch wax, containing from about 400-1500 wppm oxygen in theform of indigenous oxygenates, for the treatment, which was followed byusing the treated catalyst to hydrodewax the same waxy feed.Consequently, the oxygenates used for the treatment were present duringthe subsequent hydrodewaxing. It has also been demonstrated using a raw(untreated) Fischer-Tropsch synthesized light oil fraction containing 15wt. % oxygenates, measured as the total weight of oxygen-containingmolecules. No oxygenates were found in the hydrodewaxed hydrocarbonproducts. Hydrodewaxing occurs during the treatment, but initially notwith the higher hydrodewaxed product yield obtained after the catalysthas been treated sufficiently long enough for it to line out. This isexplained below. The wax and light oil were formed from aFischer-Tropsch hydrocarbon synthesis reaction over a non-shiftingcobalt catalyst.

If the indigenous oxygenates are not present in a sufficient amount,then additional oxygenates are simply added to the feed for thetreatment. In another embodiment, a hydrocarbon other than the feed tobe hydrodewaxed may be used as the carrier for the oxygenates treatment.For the treatment, the oxygenates will be present in an amount of atleast 100 wppm, measured as oxygen, of the hydrocarbon used for thetreatment, preferably at least 200 wppm and more preferably at least 400wppm. The presence of greater amounts of oxygenates (e.g., ≧3,000 wppm)will not adversely effect the catalyst, process or hydrodewaxedproducts. Preferred oxygenates are oxygen-containing molecules whichcomprise functional groups containing hydroxyl, alcohols, esters,ethers, ketones, aldehydes, carboxylic acids and mixtures thereof, morepreferably comprising one or more alcohols. Another preferred oxygenateis water which may be generated from other oxygenates underhydrodewaxing conditions. If one or more oxygenates are added to ahydrocarbon stream used for the treatment, they may be discontinuedafter the catalyst has lined out, which may take from two weeks to amonth. However, leaving them in the feed being hydrodewaxed does notadversely effect the hydrodewaxing reaction or the catalyst. Line outmay be determined by observing the cracking activity, as reflected in areduction in either or both gas make and extent of feed conversion tolower boiling hydrocarbons. The catalyst is considered to be lined out,when the cracking activity has been reduced to a more or less constantvalue.

The hydrodewaxing removes the oxygenates, which are therefore typicallynot found in the hydrodewaxed products. The oxygenates treatment isconducted at the same or different conditions used for the subsequenthydrodewaxing, after the catalyst has been treated. In the examplesbelow, the catalyst treatment was initiated at a temperature of almost300° F. (167° C.) below the subsequent hydrodewaxing temperature.Hydrodewaxing reaction conditions include respective temperatures,hydrogen partial pressures, liquid hourly space velocities and hydrogentreat gas rates broadly ranging from 450-850° F. (232-454° C.), 10-2,000psig (170−13891 kPa), 0.1-5.0 LHSV and 500-10000 scf/B (89-1780 m³/m³).These conditions will more typically range from 500-750° F. (260-399°C.), 100-1,000 psig (791−6996 kPa,), 0.5-3.0 LHSV, and 1000-5000 scf/B(178-890 m³/m³) with pressures of from 200-700 psig (1480-4928 kPa)preferred.

The wax or waxy hydrocarbons produced by a Fischer-Tropsch reaction arehydrodewaxed using the treated catalyst of the invention to producedewaxed products of reduced pour point comprising at least one of (i) adistillate fuel fraction and (ii) a lubricant fraction. Typically, thehydrodewaxing reduces the pour point of the hydrodewaxed product to thedesired specification to form one or more of (a) one or more distillatefuel stocks used for blending, and (b) one or more lubricant basestocks. The one or more lubricant base stocks may or may not include aheavy lubricant base stock. In a preferred embodiment, the hydrodewaxedlubricant product includes one or more lubricant base stocks and morepreferably also a heavy lubricant base stock. By distillate fuel ismeant a hydrodewaxed hydrocarbon fraction, boiling somewhere in therange of from about C₅ up to about 550-730° F. (288-388° C.) andincludes naphtha, diesel and jet fuel. In the context of the invention,the heavy fraction comprises a heavy lubricant oil fraction which, whenhydrodewaxed, comprises a heavy lubricant base stock. By lubricant basestock, is meant a lubricant oil having an initial boiling point above600° F. (316° C.) and more typically at least about 700-750° F.(371-399° C.), that has been hydrodewaxed to the desired pour and cloudpoints. A heavy lubricant base stock has an initial boiling point in therange of from about 850-1000° F. (454-538° C.), with an end boilingpoint above 1000° F. and preferably above 1050° F. (566° C.). Theinitial and end boiling points values referred to herein are nominal andrefer to the T5 and T95 cut points obtained by gas chromatographdistillation (GCD), using the method set forth below.

Distillate fuel and lubricant base stocks produced according to theinvention are typically hydrofinished at mild conditions and optionallydehazed, to improve color and stability, to form finished fuel andlubricant base stocks. As is known, haze is cloudiness or a lack ofclarity, and is an appearance factor. Dehazing is typically achieved byeither catalytic or absorptive methods to remove those constituents thatresult in haziness. Hydrofinishing is a very mild, relatively coldhydrogenating process, which employs a catalyst, hydrogen and mildreaction conditions to remove trace amounts of heteroatom compounds,aromatics and olefins, to improve oxidation stability and color.Hydrofinishing reaction conditions include a temperature of from 302 to662° F. (150 to 350° C.) and preferably from 302 to 482° F. (150 to 250°C.), a total pressure of from 400 to 3000 psig. (2859 to 20786 kPa), aliquid hourly space velocity ranging from 0.1 to 5 LHSV (hr⁻¹) andpreferably 0.5 to 3 hr⁻¹. The hydrogen hourly treat gas rate will rangefrom 250 to 10000 scf/B (44.5 to 1780 m³/m³). The catalyst will comprisea support component and at least one catalytic metal component of metalfrom Groups VIB (Mo, W, Cr) and/or iron group (Ni, Co) and noble metals(Pt, Pd) of Group VIII. The Groups VIB and VIII referred to herein,refers to Groups VIB and VIII as found in the Sargent-Welch PeriodicTable of the Elements copyrighted in 1968 by the Sargent-WelchScientific Company. The metal or metals may be present from as little as0.1 wt. % for noble metals, to as high as 30 wt. % of the catalystcomposition for non-noble metals. Preferred support materials are low inacid and include, for example, amorphous or crystalline metal oxidessuch as alumina, silica, silica alumina and ultra large pore crystallinematerials known as mesoporous crystalline materials, of which MCM-41 isa preferred support component. The preparation and use of MCM-41 isknown and disclosed, for example, in U.S. Pat. Nos. 5,098,684, 5,227,353and 5,573,657.

Fuel and lubricant base stocks respectively comprise hydrodewaxed fueland lubricant fractions boiling within the distillate fuel and lubricantoil boiling ranges, having low temperature properties, including pourand cloud points, sufficiently lower than what the respective fractionhad prior to the hydrodewaxing, to meet desired specifications orrequirements. A fuel or lubricant is prepared by forming a mixture ofthe respective stock and an effective amount of at least one additiveor, more typically, an additive package containing more than oneadditive. Illustrative, but non-limiting examples of such additives fora finished lubricant (lubricant) include one or more of a detergent, adispersant, an antioxidant, an antiwear additive, an extreme pressureadditive, a pour point depressant, a VI improver, a friction modifier, ademulsifier, an antioxidant, an antifoamant, a corrosion inhibitor, anda seal swell control additive. The stock used in forming the mixture istypically one that has been mildly hydrofinished and/or dehazed afterhydrodewaxing, to improve its color, appearance and stability. Lowtemperature property requirements will vary and some depend on thegeographical location in which the fuel or lubricant will be used. Forexample, jet fuel must have a freeze point of no higher than −47° C.Diesel fuel has respective summer and winter cloud points, varying byglobal region, from −15 to +5° C. and −35 to −5° C. Low temperatureproperties for conventional light and medium lubricant base stocks, mayinclude a pour point of about −20° C. and a cloud point typically nomore than 15° C. higher. A heavy lubricant base stock will typically beclear and bright at room temperature and pressure conditions of 75° F.(24° C.) and one atmosphere (101 kPa) pressure. However, in some casesthe cloud point may be higher than 75° F. (24° C.).

The waxy feed or wax to be hydrodewaxed comprises all or a portion ofthe waxy hydrocarbon fraction produced in a Fischer-Tropsch hydrocarbonsynthesis reactor, which is liquid at the reaction conditions. It isknown that in a Fischer-Tropsch hydrocarbon synthesis process, liquidand gaseous hydrocarbon products are formed by contacting a synthesisgas comprising a mixture of H₂ and CO with a Fischer-Tropsch catalyst,in which the H₂ and CO react to form hydrocarbons. The synthesis gastypically contains less than 0.1 vppm and preferably less than 50 vppbof sulfur or nitrogen in the form of one or more sulfur andnitrogen-bearing compounds. Methods for removing nitrogen and sulfurfrom synthesis gas down to these very low levels are known and disclosedin, for example, U.S. Pat. Nos. 6,284,807; 6,168,768; 6,107,353 and5,882,614.

In the process of the invention, the noncobalt Fischer-Tropsch catalystcomprises a catalytically effective amount of at least one of Fe, Ni,Ru, Re or Rh, preferably Fe and Ru, and optionally one or more promoterssuch as Mn, Ti, Mg, Cr, Ca, Si, Al, Cu, Th, Zr, Hf, U, Mg and La on asuitable inorganic support material, preferably one which comprises oneor more refractory metal oxides. Useful catalysts and their preparationare known and illustrative, but nonlimiting examples may be found, forexample, in U.S. Pat. Nos. 4,568,663; 4,663,305; 4,542,122; 4,621,072,5,545,674 and U.S. published application 20020128331.

Fixed bed, fluid bed and slurry hydrocarbon synthesis processes are wellknown and documented in the literature. In all of these processes thesynthesis gas is reacted in the presence of a suitable Fischer-Tropschtype of hydrocarbon synthesis catalyst, at reaction conditions effectiveto form hydrocarbons. Some of these hydrocarbons will be liquid, somesolid (e.g., wax) and some gas at standard room temperature conditionsof temperature and pressure of 25° C. and one atmosphere (101 kPa)pressure. Slurry Fischer-Tropsch hydrocarbon synthesis processes areoften preferred, because they are able to produce more of the relativelyhigh molecular weight, paraffinic hydrocarbons useful for lubricant andheavy lubricant base stocks. In the practice of the invention, the waxyhydrocarbons or wax feed may be produced in a slurry, fixed or fluidizedbed Fischer-Tropsch reactor.

Fischer-Tropsch wax contains indigenous oxygenates. For example, Table Abelow lists the ranges of indigenous oxygenates, measured as oxygen,obtained as a function of boiling range, from wax synthesized using anon-shifting catalyst comprising a rhenium promoted cobalt catalyticcomponent. In Table A, the oxygen is that from the oxygen-containingorganic compounds or oxygenates and is given as oxygen and not as thewppm or wt. % of oxygenated molecules themselves. When, for example, waxis referred to as containing from 400-600 wppm oxygenates, measured asoxygen, it means that the amount of oxygen from the oxygenates in thewax was determined to be from 400-600 wppm. The reactor wax in the tableis defined as having a boiling range of from about 500° F. (260° C.), upto more than 1,000° F. (538° C.), while the hot separator wax boils fromabout 350-700° F. (177-371° C.).

TABLE A Total Alcohols Ethers Esters Oxygen wppm wppm wppm wt. % Reactorwax  67-1259 86-270 67-109 0.06-0.2  Hot separator 1519-3394 — —0.17-0.39 wax

Table B below lists the concentrations of these three types ofoxygenates in the same kind of Fischer-Tropsch wax at three differentmolecular carbon numbers, which are representative of three differentmolecular weight ranges.

TABLE B Oxygenates, wppm Carbon Number Alcohols Ethers Esters 10 510 5 —15 240 6 — 31 105 10 12

In the illustrative, but nonlimiting examples below, the wax wasproduced in a slurry Fischer-Tropsch reactor, containing a non-shifting,rhenium promoted cobalt catalyst having a titania support component andan initial boiling point of about 450° F. (232° C.). This wax typicallycomprises 90 or more weight percent paraffins, with up to 2-4 wt. %oxygenates and up to 2-5 wt. % olefins. Aromatics were not detectable byNMR analysis and the wax contained less than 1 wppm sulfur and less than1 wppm nitrogen. The wt. % total oxygen is measured by neutronactivation. The total oxygen content may be placed on a water-free basisby measuring water content using calcium carbide (to form acetylene)followed by GC-MS if the water content is less than about 200 wppm. Forgreater than 200 wppm water content, the Karl-Fischer method in ASTMstandard D-4928 is used. The total oxygenate content is determined byhigh-resolution NMR, while primary alcohols, ketones and aldehydes aredetermined by GC-MS. Acids, esters and other dioxygenates are determinedby IR or GC-FID and GC-MS. Aromatics are determined by X-RayFluorescence (XRF), as described in ASTM Standard D-2622, while olefinsare determined using a Bromine Index, determined by coulimetric analysisper ASTM standard D-2710. Sulfur is measured by XRF as per ASTM standardD-2622 and nitrogen by syringe/inlet oxidative combustion withchemiluminescence detection per ASTM standard D-4629.

In the integrated process embodiment for synthesizing and dewaxing waxyhydrocarbons, the process comprises reacting H₂ and CO in the presenceof a Fischer-Tropsch hydrocarbon synthesis catalyst at reactionconditions effective to form waxy hydrocarbons, a portion of which areliquid at the reaction conditions, hydrodewaxing at least a portion ofthese waxy hydrocarbons in the presence of hydrogen and an unsulfidedcatalyst comprising a hydrogenation component and a dewaxing component,wherein the catalyst has been reduced and then treated with ahydrocarbon stream containing one or more oxygenates, prior tohydrodewaxing, to (i) increase the catalyst's selectivity forhydrodewaxing, (ii) reduce gas make during hydrodewaxing, and (iii)produce dewaxed hydrocarbons reduced in pour and cloud point. Byhydrogen is meant hydrogen, a hydrogen hourly treat gas or ahydrogen-rich tail gas comprising at least 60 and preferably at least80% hydrogen, with the remainder being inert with respect to thehydrodewaxing catalyst and the hydrocarbon synthesis catalyst upstream.Hydrogen or a hydrogen treat gas with such low sulfur levels can beobtained from various sources, including but not limited to treating aslip stream of the synthesis gas (e.g., a methanator or shift reactor,TSA, PSA, membrane separation and the like, as is known and disclosed,for example, in U.S. Pat. No. 6,147,126) to remove CO from the synthesisgas and produce a high quality hydrogen gas.

The invention will be further understood with reference to the examplesbelow.

EXAMPLES

In Example 1, the oxygenates-containing hydrocarbon used to treat thereduced ZSM-48 hydrodewaxing catalyst was a Fischer-Tropsch wax, whilein Example 2 it was an oxygenates-containing light oil that was alsoproduced in the Fischer-Tropsch hydrocarbon synthesis reactor. Both weresynthesized together in a slurry Fischer-Tropsch reactor, in which theH₂ and CO were reacted in the presence of a titania supported,rhenium-promoted cobalt catalyst to form hydrocarbons, most of whichwere liquid at the reaction conditions. The oxygenates in both the waxand light oil were also formed in the hydrocarbon synthesis reactor as aconsequence of the synthesis reaction, and were therefore indigenous tothe wax and oil. These oxygenates were mostly alcohols, along with minoramounts of esters and ethers. The wax, which was solid at ambientconditions, comprised a 450° F.+(232° C.) waxy fraction described belowand contained from 400-600 wppm oxygenates measured as oxygen. The lightoil, which was liquid at ambient conditions, comprised from about C₅-C₂₀molecules, had a boiling range of about 97-526° F. (36-274° C.) andcontained about 7010 wppm oxygenates, measured as total oxygen content,as alcohols, esters and organic acids. About 5.2 wt. % of the light oilcomprised normal alcohols as ethanol, propanol, hexanol, heptanol,octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, pentanoland hexadecanol.

Wt. % Boiling Point Distribution of Fischer-Tropsch Reactor Waxy Feed450+ (232° C.+) 98 700° F.+ (371° C.+) 71.5 1000° F.+ (538° C.+)  26.2

In addition to the oxygenates-containing wax and light oil used to treatthe reduced dewaxing catalyst, a 320° F.+(160° C.) and a 700° F.+(371°C.) waxy isomerate were used (i) to contact the reduced catalyst as acomparison to the oxygenates treatment of the invention and (ii) as waxyfeeds for the hydrodewaxing in Example 1. The waxy isomerates containedno oxygenates, and those used in Example 1 were obtained byhydrodewaxing an oxygenates-containing 450° F.+(232° C.) Fischer-Tropschwax over a catalyst comprising 0.3 wt. % Pd on an amorphous silicaalumina support. For Example 2 a light isomerate having a boiling rangeof from about 700-950° F. (371-510° C.) was used. The isomerizationremoved all the oxygenates from the wax. The light isomerate wasobtained using a ZSM-48 catalyst. All three isomerate fractions stillcontained some wax after the isomerization. For example, the lightisomerate had a +14° C. pour point and produced 22 wt. % wax whensolvent dewaxed with MIBK at −18° C.

In all the examples below, the waxy feed was hydrodewaxed over aparticulate ZSM-48 catalyst and the hydrogen treat gas was purehydrogen. The ZSM-48 catalyst comprised 0.6 wt. % Pt as thehydrogenating component, on a composite of the hydrogen form of theZSM-48 zeolite and an alumina binder. The hydrogen form ZSM-48 zeolitecomponent of the catalyst was prepared according to the procedure inU.S. Pat. No. 5,075,269, the disclosure of which is incorporated hereinby reference. The Pt component was added by impregnation, followed bycalcining. The calcined particles were loaded into a fixed bed pilotplant reactor and reduced with flowing hydrogen in-situ in the reactor.The temperature was then lowered and the reduced catalyst was treated byslowly (to avoid exotherms) introducing the hot liquid wax into thereactor over a period of about six hours, to insure all the reducedcatalyst particles were immersed in the waxy liquid and thereforecontacted by the oxygenates. After this, the temperature in the reactorwas raised to the hydrodewaxing temperature and the feed to be dewaxedpassed into it. The hydrogen flow into the reactor was maintained duringthe treatment and subsequent hydrodewaxing. The pour point andconversion data in the Figures were taken after the reactor had linedout, which typically took about 30 days.

The 700° F.+(371° C.) yields and pour points in the Figures refer tothose for the hydrodewaxed (isomerized) 700° F.+(371° C.) fraction. TheCH₄/iso-C₄H₁₀ ratio is a mole ratio and is a measure of hydrogenolysis(CH₄ make) to beta scission (iso-C₄H₁₀ make). The gas make is the weightpercent of feed converted to C₁-C₄ hydrocarbons. The 700° F. (371° C.)conversion is the weight percent of the 700° F.+(371° C.) feed materialconverted to hydrocarbons boiling below 700° F. (700° F./(371° C.)). The700° F.+(371° C.) yield vs. pour point refers to the weight percentyield of isomerized hydrocarbons boiling above 700° F. (371° C.), at afeed conversion level to the corresponding pour point on the graph. The700° F.+(371° C.) conversion is calculated as follows:

700° F.+conversion=[1−(wt. % 700° F.+fraction in product)/(wt. % 700°F.+in feed)]×100

Gas chromatograph distillations (GCD) were conducted using a hightemperature GCD method modification of ASTM D-5307. The column consistedof a single capillary column with a thin liquid phase, less than 0.2microns. External standards were used, consisting of a boiling pointcalibrant ranging from 5 to 100 carbons. A temperature programmedinjector was used and, prior to injection, the samples were gentlywarmed using hot water. Boiling ranges were determined using this methodand the T5 and T95 GCD results. Cloud point values were measured usingASTM D-5773 for Phase Two Tec Instruments under the lubricant proceduremethod. Pour point was measured according to ASTM D-5950 for ISL AutoPour Point measurement. Viscosity and viscosity index were measuredaccording to the ASTM protocol D-445 and D-2270, respectively.

Example 1 Treated Catalyst

The ZSM-48 catalyst was reduced for six hours in flowing hydrogen, at atemperature of 500° F. (260° C.) and a pressure of 500 psig (3549 kPa).The hydrogen flow rate was a gas hourly space velocity (GHSV) of 445.Following reduction and while maintaining the hydrogen flow andpressure, the temperature was reduced to 350° F. (177° C.), and then theFischer-Tropsch 450° F.+(232° C.) oxygenates-containing liquid wax wasslowly introduced into the reactor over a period of six hours to treatthe catalyst. While maintaining the pressure, hydrogen and anoxygenates-containing wax flow rate of 1 LHSV into the reactor, thetemperature was raised to a hydrodewaxing temperature range of 610-630°F. (321-332° C.) and dewaxing continued for 50 days. Then the feed wassequentially switched to 320° F.+(160° C.) and 700° F.+(371° C.+) waxyisomerates for 45 days. These isomerates had previously been partiallyhydrodewaxed, did not contain oxygenates and were obtained byhydrodewaxing oxygenates-containing Fischer Tropsch wax. The results forthis treated catalyst are shown in FIGS. 1-6.

FIG. 1 shows the very low hydrogenolysis to beta scission ratio(CH₄/iso-C₄H₁₀) for the treated catalyst of the invention duringhydrodewaxing the much greater ratio incurred using the untreatedcatalyst of Comparative Example A. The open squares at day 60 correspondto the start-up of the treated catalyst on the oxygenates-containing waxfeed. After only about six days of hydrodewaxing, the beta scissionratio was less than 0.5. The solid circles at day 115 correspond to thestart up of the untreated catalyst of Comparative Example A. At the sametime the untreated catalyst was started up, the feed for the treatedcatalyst was switched to the non-oxygenate, waxy isomerate feeds. Thelined out behavior for the treated catalyst of the invention isunchanged by the feed switchover at about the 115^(th) day. In contrast,the behavior of the untreated catalyst is very different at start up.The beta scission ratio is high, in excess of 6, and drops more slowlywith time. The scatter in the data observed with the untreated catalystof Comparative Example A is due to changes in temperature. However, thetreated catalyst of the invention underwent the same temperature changesat this time and does not exhibit scatter.

FIG. 2 compares gas make as a function of 700° F.+(371° C.+) feedconversion to lower boiling hydrocarbons (700° F.−(371° C.−)) for thetwo catalysts. Over the entire conversion range, the untreated catalystof Comparative Example A had higher gas make, shown as circles, than thetreated catalyst of the invention, shown as open squares.

FIG. 3 compares the 700° F.+(371° C.+) dewaxed oil yield as a functionof pour point. For a given pour point target, it shows the dewaxed oilyield is substantially greater using the treated catalyst of theinvention.

Comparative Example A Untreated Catalyst

This example was similar to Example 1, except for the treatment of thereduced catalyst. In this experiment, instead of treating the reducedcatalyst with the oxygenates-containing, Fischer-Tropsch wax, thereduced catalyst was immersed in the 320° F.+(160° C.+), oxygenates-freewaxy isomerate for 6 hours. Then, as in Example 1, the temperature wasraised to a hydrodewaxing range of 570-620° F. (299-327° C.). Thehydrodewaxing reaction was run for 45 days, during which time the fedwas switched from the 320° F.+(160° C.+) isomerate, to the 700° F.+(371°C.+) isomerate (also free of oxygenates). The results are shown in FIGS.1-3 and discussed above in Example 1.

Comparative Example B Sulfided Catalyst

In this experiment, the calcined catalyst was reduced as in Example 1and then sulfided, by treating it with 2% hydrogen disulfide in hydrogenat 700° F. (371° C.+) and 500 psig (3549 kPa) for four hours. Followingsulfiding, it was placed on stream with the oxygenates-free, 320°F.+(160° C.+) waxy isomerate for about 20 days at temperatures between540-580° F. (282-304° C.), using pure hydrogen at 2500 SCF/B and 500psig. (3549 kPa). The waxy isomerate feed rate was 1 LHSV. Then the feedwas switched to the 450° F.+(232° C.) oxygenates-containingFischer-Tropsch wax and run for an additional 84 days at the sameconditions. The results are shown as compared to the treated catalyst ofthe invention of Example 1, in FIGS. 4, 5 and 6.

The results for the ratio of hydrogenolysis to beta scission are shownin FIG. 4. The sulfided catalyst is shown as the closed diamonds and theoxygenates treated catalyst of the invention of Example 1 as opensquares. The sulfided catalyst lined out to a ratio of less than 0.5almost immediately, while it took several days for the treated catalystof the invention to reach the same ratio. However, after line out wasreached, both catalysts were about the same.

FIG. 5 shows the total gas make for both catalysts is similar after lineout. On day 60 both catalysts were on the oxygenated feed and were bothundergoing a series of temperature changes. Nevertheless, both areexperimentally indistinguishable after line out. FIG. 6 shows the pourpoint-conversion data for both catalysts is virtually indistinguishablewithin experimental error.

Example 2 Treated Catalyst

This experiment was similar to that of Example 1 in all respects, exceptthat (i) after the treatment the raw wax was dewaxed for only 6 days at600° F. (316° C.) and 500 psig (3549 kPa) hydrogen, then (ii) thepressure was reduced, to 250 psig (1825 kPa), and dewaxing continued foranother 25 days, before the feed was switched from the raw wax to thelight isomerate described above, which was dewaxed at 600° F. (316° C.)and 250 psig (1724 kPa). The dewaxing results for the light isomerateare shown in FIGS. 7 and 8.

Example 3 Treated Catalyst

This experiment was similar to that of Examples 1 and 2, except that thecatalyst was reduced at 250° F. (121° C.) and 250 psig (1825 kPa),instead of 500° F. (260° C.) and 500 psig (3549 kPa) and, prior tohydrodewaxing, instead of the oxygenates-containing wax, theoxygenates-containing light oil described above was used to treat thereduced catalyst at 250 psig. (1724 kPa) and 350° F. (177° C.). Then thetemperature was increased to 600° F. (316° C.) and the feed slowlyswitched to the 700-950° F. (371-482° C.) cut of isomerate feed, over aline-out time of only 14 days. The dewaxing results for the lightisomerate dewaxed by the catalyst treated by the light oil of thisexample are shown in FIGS. 7-8.

Referring now to FIGS. 7 and 8, it is seen that there is essentially nodifference between using an oxygenates-containing light oil and anoxygenates-containing wax to treat the ZSM-48 dewaxing catalyst. This isreflected in the conversion vs. pour point and gas make dewaxing resultsbeing essentially the same for both.

Example 4 Other Catalysts

Catalytic dewaxing was conducted at 750 psig (5272 kPa) H₂, 1.0 LHSV,gas treat rate of 2500 SCF/BBL (445 m³/m³). 5 cc of catalyst was crushedto 14/35 mesh and mixed with diluent. The feed for all of the catalystswas a hydroisomerized Fischer Tropsch wax, which was fractionated toproduce a feed which is nominally 700° F.+ with a wax content of 6.42%as measured by solvent dewaxing with 100% MIBK.

The catalysts tested all had 0.5 wt. % platinum as the dehydrogenatedcomponent, except Z-876A which was 0.3 wt. % Pt and 0.15 wt. % Pd.Operating temperatures ranged from 550° F. (288° C.) to 580° F. (304°C.). The products from the various catalysts were analyzed for pourpoint and viscosity and the data is included in the table below. Theyields shown in the table correspond to those obtained over operation ofthe listed catalyst alone. These results show the performance of thesecatalysts without oxygenate treatment for the dewaxing of FischerTropsch derived isomerates. The lubes produced from these catalysts showreasonable viscosities and pour points. The addition of oxygenates tothese catalysts would be expected to produce a yield enhancement similarto that shown in previous examples for the selective catalytic dewaxingin the production of lubes using ZSM-48.

TABLE C Catalyst 700° F.+ Yield KV@100° C. VI Pour Point ° C. Pt/TON94.49 5.1 148 −21 Pt/ZSM-23 90.18 5.22 147 −27 Z-876 (FER) 64.9 4.74 141−44 Pt/FER 59.38 4.68 141 −38 Pt/LaFER 89.24 4.76 142 −33In Table C, TON is theta-1 (ZSM-22) and FER is ferrierite.

1. An unsulfided hydrodewaxing catalyst comprising a Group VIII metalcomponent and a dewaxing component wherein said catalyst is made byreduction and then treatment with a stream containing one or moreoxygenates, and wherein said metal is Pt, Pd or mixtures thereof.
 2. Acatalyst according to claim 1 wherein the hydrocarbon used for saidtreatment is produced over a noncobalt Fischer-Tropsch catalyst.
 3. Acatalyst according to claim 2 wherein the noncobalt catalyst is at leastone of Fe, Ni, Ru, Re or Rh.
 4. A catalyst according to claim 3 whereinthe noncobalt catalyst is Fe or Ru.
 5. A catalyst according to claim 4wherein said oxygenates comprise one or more oxygen containingmolecules.
 6. A catalyst according to claim 5 wherein said oxygenatescomprise one or more functional groups containing hydroxyl, mono andpolyhydric alcohols, esters, ethers, ketones, aldehydes, carboxylicacids, and mixtures thereof.
 7. A catalyst according to claim 6 whereinsaid one or more oxygenates are present in said treating hydrocarbon inan amount of at least 100 wppm, measured as oxygen.
 8. A catalystaccording to claim 7 wherein said one or more oxygenates are present insaid treating hydrocarbon in an amount of at least 200 wppm, measured asoxygen.
 9. A catalyst according to claim 8 wherein the hydrodewaxingcatalyst contains at least one molecular sieve.
 10. A catalyst accordingto claim 9 wherein the molecular sieve is at least one of ZSM-5, ZSM-11,ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-57, ferrierite, EU-1, NU-87, ITQ-13or MCM-71, and wherein the molecular sieve contains at least one 10 or12 ring channel.
 11. A catalyst according to claim 10 wherein themolecular sieve is ZSM-48.
 12. A catalyst according to claim 9 whereinthe molecular sieve is at least one of zeolite beta, ZSM-12, MCM-68,ZSM-18, offretite, mordenite or faujasite. 13-63. (canceled)